Coated wood substrate

ABSTRACT

The invention includes a method for preparing and top coating an item made of powder coated MDF (or other substrate containing wood) with the end result of improved visual and tactile smoothness; the invention includes the steps of cutting and machining the part, pre-powder preparation and sanding of the part, powder coating the part, post-powder preparation and sanding, and applying the liquid top coat to the part, resulting in a smoother finish than is currently available in any other powder coated MDF finish while requiring less coats than similar liquid paint finishes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 13/795,600 filedMar. 12, 2013, entitled “Method for Preparing and Top Coating a PowderCoated Wood Substrate”, which is hereby fully incorporated herein byreference.

TECHNICAL FIELD

The invention relates to a method of powder coating materials. Morespecifically, the invention relates to a process of taking a part madeof powder coated MDF (or other substrate containing wood) and preparingit to accept a top coat of liquid finish, with the end goal of enhancingthe final smoothness of finish.

BACKGROUND

Powder coating is a type of coating that is applied as a free-flowing,dry powder. The main difference between a conventional liquid paint anda powder coating is that the powder coating is stored as a solid anddoes not need to be kept in a liquid form (using such liquids as a waterbase or solvent) in order to keep the binder and filler particles insuspension. The coating is typically applied electrostatically and isthen cured under heat to allow it to flow and form a “skin” around allor part of the substrate. The powder may be a thermoplastic, thermoset,or UV polymer. It is usually used to create a hard finish that istougher than conventional paint. Powder coating is mainly used forcoating of metals, such as household appliances, aluminum extrusions,and automobile and bicycle parts. Newer technologies allow othermaterials, such as MDF (medium-density fiberboard), to be powder coatedusing different methods.

There are several advantages of powder coating over conventional liquidcoatings:

-   -   1. Powder coatings emit zero or near zero volatile organic        compounds (VOC).    -   2. Powder coatings can produce much thicker coatings in one coat        than conventional liquid coatings without running or sagging.    -   3. Powder coating overspray can be recycled and thus it is        possible to achieve nearly 100% use of the coating.    -   4. Powder coating production lines typically produce less        hazardous waste than conventional liquid coatings.    -   5. A wide range of specialty effects is easily accomplished        which would be impossible to achieve with other coating        processes.

While powder coatings have many advantages over other coating processes,there are some disadvantages to the technology. Although the powder isrelatively easy to apply in a single thick coating, a single powder coatis not as smooth as a similarly thick liquid paint finish; however, toachieve a similarly thick liquid paint finish it is necessary to applymultiple coats with sanding between each coat. Furthermore, theapplication of multiple powder coats serves to further increase thethickness of the coating, but does not reliably enhance the visual ortactile smoothness of the powder coated finish.

Many manufacturers of powder coated MDF have taken various steps in thepast in order to improve the smoothness of the finish. Methods include:

-   -   1. Varying the preheat and cure temperature settings    -   2. Additional pre-coating sanding, both manual and automated    -   3. Installation of infrared heaters or UV curing lights at        various points in the powder coating line    -   4. Reformulation of powder used in the coating process    -   5. Polyester versus epoxy base of the powder coating (chemistry        adjustments)    -   6. Increased fineness of powder grind    -   7. Repeated sifting of powder during formulation    -   8. Automated versus hand spraying and measurement of application

The aforementioned methods have indeed resulted in incrementallyincreased smoothness relative to previously existing methods. Employingany or all of these methods, however, results in a maximum surfacesmoothness in the 4-6 range on the PCI scale.

In such industries as furniture and cabinetry, there is growing demandfor increasingly smooth finishes. Traditionally, this demand has beenmet through such finishes as laminates, veneers, vinyl wraps, or liquidpaints. These traditional finishes have their own shortcomings andpowder coated MDF is frequently a more desirable choice for durabilityor part design needs. However, it is not possible to achieve similarsmoothness in powder coated MDF finishes regardless of content or steps.

Therefore, there exists a need for a method of preparing and top coatingan item made of powder coated MDF that enhances visual and tactilesmoothness.

SUMMARY

The invention relates to a method for preparing and top coating an itemmade of powder coated MDF in order to enhance visual and tactilesmoothness. In one embodiment, the invention includes the steps ofcutting and machining the part, pre-powder preparation and sanding ofthe part, powder coating the part, post-powder preparation and sanding,and applying the liquid top coat to the part.

In another embodiment, the method includes the steps of obtaining a partthat is fabricated from a substrate containing wood, cutting andmachining the part to a desired size utilizing equipment that has atolerance that is less than +/−0.030″. Next, the part undergoespre-powder preparation and sanding by utilizing a sander to smooth thefaces and edges of the part, whereby the sander has a Y-axis toleranceof less than 0.003″, and wherein the edges are sanded to a minimumradius of 1/32″ (0.8 mm). Next, the part is powder coated whereby thepart is coated with at least 5 mils of coverage about its surfaces andedges. The part then undergoes post-powder preparation and sanding usingan abrasive, whereby the edges and faces of the part are sanded to a PCIsmoothness of at least 7. Lastly, a liquid top coat is applied to thepart to achieve a minimum top coat thickness of 2 wet mils.

In an alternative embodiment, the invention includes a method for powdercoating a part to enhance visual and tactile smoothness. The methodincludes the steps of obtaining a part that is fabricated frommedium-density fiberboard, cutting and machining the part to a desiredsize utilizing equipment that has a tolerance that is less than+/−0.030″, pre-powder preparation and sanding of the part by utilizing asander to smooth the faces and edges of the part, whereby the sander hasa Y-axis tolerance of less than 0.003″, and wherein the edges are sandedto a minimum radius of 1/32″ (0.8 mm), and wherein the part is firstsanded with a 220 grit aluminum oxide, silicon carbide media, thensanded with a 280 grit aluminum oxide, silicon carbide media, thensanded with a 320 grit aluminum oxide, silicon carbide media. The partis then powder coated, whereby the part is heated to a consistenttemperature to create an electrostatic charge, wherein powder is appliedto the part and the part is then allowed to cure, resulting in a partthat is coated with at least 5 mils of coverage about its surfaces andedges. Next, the part undergoes post-powder preparation and sandingusing an abrasive having a minimum grit size of 15μ, whereby the edgesof the part are sanded and whereby the faces of the part are sanded to aPCI smoothness of at least 7. Lastly, a liquid top coat is applied tothe part to achieve a minimum top coat thickness of 2 wet mils; wherebythe finished part has a PCI smoothness of at least 7.

In yet another alternative embodiment, the invention includes an articlehaving enhanced visual and tactile smoothness. The article comprises asubstrate containing wood. A surface coating with PCI smoothness of atleast 7 is formed on the surface of the article by the process ofcutting and machining the part to a desired size utilizing equipmentthat has a tolerance that is less than +/−0.030, pre-powder preparationand sanding of the part by utilizing a sander to smooth the faces andedges of the part, whereby the sander has a Y-axis tolerance of lessthan 0.003″, and wherein the edges are sanded to a minimum radius of1/32″ (0.8 mm). Next, the part is powder coated whereby the part iscoated with at least 5 mils of coverage about its surfaces and edges.Next, the part undergoes post-powder preparation and sanding using anabrasive, whereby the edges and faces of the part are sanded to a PCIsmoothness of at least 7. Next, a liquid top coat is applied to the partto achieve a minimum top coat thickness of 2 wet mils. Compared withuntreated powder coated MDF, the resulting finish is significantlysmoother than other known powder coated finishes.

The idea of a top coat over powder coated MDF in order to enhancesurface smoothness is novel and is not known to have been employedbefore the conception of this invention; further, it results in asmoothness rating in the range of 8-10 on the PCI scale, a smoothnessthat is not currently attainable with existing powder coated MDFfinishes.

The above summary is not intended to describe each illustratedembodiment or every implementation of the subject matter hereof. Thefigures and the detailed description that follow more particularlyexemplify various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Subject matter hereof may be more completely understood in considerationof the following detailed description of various embodiments inconnection with the accompanying figures, in which:

In order for the advantages of the invention to be readily understood, amore particular description of the invention briefly described abovewill be rendered by reference to specific embodiments that areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are not thereforeto be considered to be limiting of its scope, the invention will bedescribed and explained with additional specificity and detail throughthe use of the accompanying drawings, in which:

FIG. 1 illustrates MDF parts that have been cut on a CNC router machine;

FIG. 2 illustrates MDF parts that have received the pre-powder coatingpreparation and sanding steps according to the invention;

FIG. 3 illustrates the step of inserting the powder coated part into thewide belt veneer segmented platen sander according to the invention;

FIG. 4 illustrates orange peel, viewable at an angle, that has beenpartially sanded down after the wide belt, according to the invention;

FIG. 5 illustrates another view of the sanded orange peel after the widebelt, according to the invention;

FIG. 6 illustrates the step of sanding the part with a random orbitalhand sander in accordance with one embodiment of the invention;

FIG. 7 illustrates a view of sanding the edge of the part with a randomorbital hand sander in accordance with one embodiment of the invention;

FIG. 8 illustrates a view of sanding the part with a random orbital handsander wherein the sanding process is almost complete and the part isready for application of the liquid top coat. There is no more visibleorange peel;

FIG. 9 illustrates a view of the part after sanding is complete andready for liquid top coat;

FIG. 10 illustrates the process steps and decision points in accordancewith the present invention;

FIG. 11 illustrates examples of inside and outside radii on a powdercoated MDF part;

FIG. 12 illustrates the ideal abrasive grit sequences for pre-powdercoating sanding in the preferred embodiment of the invention;

FIG. 13 illustrates the ideal abrasive grit sequences for post-powdercoating sanding in the preferred embodiment of the invention;

FIG. 14 illustrates a rank order of the various liquid top coats thathave been tested in accordance with the present invention; and

FIG. 15 illustrates the sanding grit sequences used in the example andcomparative examples.

While various embodiments are amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the claimedinventions to the particular embodiments described. On the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the subject matter as defined bythe claims.

DETAILED DESCRIPTION OF THE DRAWINGS

Various embodiments of systems, devices, and methods have been describedherein. These embodiments are given only by way of example and are notintended to limit the scope of the claimed inventions. It should beappreciated, moreover, that the various features of the embodiments thathave been described may be combined in various ways to produce numerousadditional embodiments. Moreover, while various materials, dimensions,shapes, configurations and locations, etc. have been described for usewith disclosed embodiments, others besides those disclosed may beutilized without exceeding the scope of the claimed inventions.

Persons of ordinary skill in the relevant arts will recognize that thesubject matter hereof may comprise fewer features than illustrated inany individual embodiment described above. The embodiments describedherein are not meant to be an exhaustive presentation of the ways inwhich the various features of the subject matter hereof may be combined.Accordingly, the embodiments are not mutually exclusive combinations offeatures; rather, the various embodiments can comprise a combination ofdifferent individual features selected from different individualembodiments, as understood by persons of ordinary skill in the art.Moreover, elements described with respect to one embodiment can beimplemented in other embodiments even when not described in suchembodiments unless otherwise noted.

Although a dependent claim may refer in the claims to a specificcombination with one or more other claims, other embodiments can alsoinclude a combination of the dependent claim with the subject matter ofeach other dependent claim or a combination of one or more features withother dependent or independent claims. Such combinations are proposedherein unless it is stated that a specific combination is not intended.

Any incorporation by reference of documents above is limited such thatno subject matter is incorporated that is contrary to the explicitdisclosure herein. Any incorporation by reference of documents above isfurther limited such that no claims included in the documents areincorporated by reference herein. Any incorporation by reference ofdocuments above is yet further limited such that any definitionsprovided in the documents are not incorporated by reference hereinunless expressly included herein.

For purposes of interpreting the claims, it is expressly intended thatthe provisions of 35 U.S.C. § 112(f) are not to be invoked unless thespecific terms “means for” or “step for” are recited in a claim.

The invention relates to a method for preparing and top coating an itemmade of powder coated MDF in order to enhance visual and tactilesmoothness. Compared with untreated powder coated MDF, the resultingfinish is significantly smoother than existing known methods:

-   -   1. Untreated powder coated MDF is able to achieve a PCI        smoothness of 4-6.    -   2. Top coated over untreated powder coated MDF is able to        achieve a PCI smoothness of 4-6.    -   3. Buffed untreated powder coated MDF is able to achieve a PCI        smoothness of 4-6.    -   4. Top coated over treated powder coated MDF, in accordance with        the present invention, is able to achieve a PCI smoothness of        8-10, by using a liquid top coat to seal the treated surface        finish.

For the purposes of this application, “smoothness” refers to the visualdetectability of smoothness or lack of a rough texture, known as “orangepeel” in a finished surface. ACT Test Panels Inc. manufacturers the PCIsmoothness scale for powder coated finishes. This scale is commonlyemployed by a wide variety of industries to compare visual smoothness ofpainted finishes. The scale ranges from 1-10, with 1 being a heavytexture and 10 being completely smooth (glass-like). For the purposes ofthis application, “failure” is meant to describe a situation resultingin a less-than-ideal finish. Failures can include situations such assanding through the coating to the bare substrate, or a final smoothnessthat is less than PCI 8-10; PCI 8-10 is a smoothness range which ishigher than is currently attainable with any other existing untreatedpowder coated MDF finish. For the purposes of this application,“untreated” refers to a standard powder coated MDF part that has notbeen modified in any way after the standard coating has been applied.“Treated” refers to powder coated MDF parts that have received theadditional steps outlined in this application.

The overall process and decision points involved in the presentinvention is shown in FIG. 10. However, there are five basic steps inthe process of the present invention. First, the part is machined andcut to the desired size. Second, the part receives a pre-powderpreparation and sanding. Third, the part undergoes a powder coatingprocess. Fourth, the part undergoes post-powder preparation and sanding.Lastly, a liquid top coat is applied to the part. With respect to theprocess of the present invention, the preferred substrate is MDF;however, similar results can be achieved with the process described onother substrates with wood content (such as high density fiberboard).Therefore, other substrates containing wood could be used whileremaining within the scope of the invention.

The first step of cutting and machining the part will now be discussed.In this step, MDF components are machined (cut to drawn shapes anddesigns) from purchased sheet stock in powder coat grade, available froma variety of milling operations. Parts cut from MDF on a CNC machine areshown in FIG. 1. MDF sheet brands and thicknesses are variable and arenot critical to this process. Machining operations generally utilizesuch equipment as CNC routers, CNC point-to-point drilling/millingequipment, through feed molding machines, shapers, hand routers, panelsaws, sliding table saws, and fixed table saws. The parts to be coatedcan be any shape designed from flat sheet material, provided the designfits within tolerances and parameters outlined herein.

Success of the sanding, preparation, coating, and post-coating processesis dependent on the initial quality of the machining. “Quality ofMachining” is defined as:

-   -   In a preferred embodiment, the tolerance of the equipment        cutting the profile is less than +/−0.030″        -   Any cuts outside of tolerance will result in a part that is            larger or smaller than expected in certain places. This            means that, during the post-powder sanding process, there is            a risk of sanding through the powder coat to the raw wood            substrate. This would result in a failure of the part, as            the part would be rendered useless.    -   In a preferred embodiment, tooling for this process is in new        condition        -   Tooling is the equipment that actually makes the cuts in the            wood. It is optimal that the tooling is in new condition so            that it is as sharp and accurate as possible. Otherwise,            inconsistent cuts will result and uneven sanding or top coat            application will be the outcome.    -   In a preferred embodiment, the tooling is constructed of solid        carbide or high speed steel        -   Solid carbide and high speed steel tooling is sharper than            standard diamond tooling, resulting in a smoother and more            reliable cut. Smoother, more reliable cuts result in a more            even surface and decrease the chance or part failure during            post-powder sanding.        -   Standard diamond tooling is less preferred because it is            generally not sharp enough to reliably achieve similar            smoothness of cut required for successful finishing without            imperfections from fiber pop. Fiber pop is a failure wherein            the fibers of the boards “pop up” during heating, resulting            in an uneven surface and increasing the chance of part            failure during post-powder sanding. Although standard            diamond tooling could theoretically be used, it increases            the likelihood of part failure.

The second step of pre-powder coating preparation and sanding of thepart will now be discussed. The face and edge preparation treatments areimportant to the final quality and appearance of the finished parts, andshould be considered as part of this invention; this step is material tothe invention because omission of the step can leave surfaceirregularities and contamination on the surface of the board to becoated. These irregularities are subsequently covered by the powdercoating but can then be exposed when sanding after powder coating. Theresult is an increased probability of sanding through to the surfacecontamination, demonstrating visible speckling or color irregularity andresulting in a part failure. Parts that have been appropriately sandedas described are illustrated in FIG. 2.

In this pre-powder coating preparation and sanding step, the part facesare sanded using a wide belt sander, a wide belt veneer segmented platensander, a wide orbital machine sander, a random orbital hand sander, ora combination of this sanding (or other surface smoothing) equipment.Grit types and sizes can vary based upon the abrasive manufacturer andthe equipment being utilized. The edges are prepared in a similar mannerwith like grit materials using machine edge sanding equipment utilizingbelts, disks, profiled sanding heads or other sanding techniquesspecific to the machine manufacturer and dictated by suitability withshape of part being sanded. The specific abrasive material,manufacturer, and equipment is not critical and can be varied whileremaining within the scope of the invention.

The following steps should ideally be taken to ensure proper pre-powdercoating part preparation:

-   -   In a preferred embodiment, abrasive grit sequence is applied in        accordance with the grit sequence table in FIG. 12.    -   In a preferred embodiment, automated edge sanding machines        should have a Y-axis tolerance of less than 0.003″ to avoid        sanding through the powder coated base finish.    -   In a preferred embodiment, manual (hand) sanding equipment        should be held flat (parallel) to the surface being sanded in        order to avoid sanding through the powder coated base finish.    -   In a preferred embodiment, edges generally should not be        designed with deeply machined profiles, as it is generally        necessary for sanding equipment to reach all parts of the face        and edges to achieve uniform quality of finish. Deeply machined        profiles are difficult to reach with sanding equipment,        increasing the probability that an area of the part is left        without being sanded. Regions of the part that are not sanded        can result in a finish that is less than optimal and that has a        higher potential part failure rate. Specific depth parameters        depend upon the sanding equipment being applied, but it is        necessary for the entire part to be sanded, otherwise the top        coat adhesion will fail.    -   In a preferred embodiment, edges of the components should        preferably have a minimum radius of 1/32″ (−0.8 mm) to avoid        “burning through” the edges with sanding equipment.    -   In a preferred embodiment, inside profiles (also known as radii)        should be designed to accommodate for edge machine sanding        capabilities. FIG. 11 depicts examples of inside and outside        radii. These specific radii criteria are dependent on the type        of edge sanding equipment milling stations available or chosen        at machine purchase.        -   This parameter is important because the part should be            properly sanded in all areas to receive the final liquid top            coat.

The step of powder coating the MDF substrate will now be discussed.There are a variety of known methods to powder coat components machinedfrom MDF. The overall process described herein can be applied to knownpowder coated MDF finishes in general, regardless of basic powdercoating method used. A powder coated MDF finish can be obtained byheating the substrate to a consistent temperature in order to create anelectrostatic charge, applying the powder, and allowing it to cure.Alternately, ultraviolet light can be used to coat the part via aUV-cured powder coating process while remaining within the scope of theinvention. As previously described, the method of powder coating is notcritical to the overall invention described herein. The preferredembodiment in these steps is that surfaces and edges should optimallyhave at least 7-8 mils of coating coverage; otherwise, post coatingsanding may sand through the coating, exposing the raw wood substrateand resulting in a failure.

A main reason why powder coating is critical to the process of thepresent invention is that powder coating results in a thicker coatingper coat on a wood substrate than liquid paints. Furthermore, the powdercoated finish is harder than that of a liquid paint, so it can be sandedmore consistently without “burning through” the coating. It istheoretically possible that 5-8 mils of paint thickness could beachieved using a liquid paint, but it would require multiple basecoats—in many cases, at least 4-6 base coats. Comparatively, powdercoatings with a thickness of 5-8 mils can routinely be achieved using aone-pass (one coat) powder coat process.

The step of post-powder preparation and sanding of the coated part willnow be discussed. After the powder coat is applied, it is optimal tofollow specific steps of the sanding process as described herein inorder to achieve the desired finish. This is one of the most criticalaspects of the entire process of the present invention.

In the preferred embodiment of this step, the edges of the part aresanded first, using an abrasive method as shown in FIG. 7. The edgesanding equipment and methodology used is variable and can vary basedupon the shape of the edge profile by those skilled in the art. In apreferred embodiment, a profile sander is utilized in accordance withgrit sequences set forth in FIG. 13 for the corresponding equipment.Successful testing has been conducted as well using a random orbitalsander in accordance with the grit sequences set forth in FIG. 13 forthe corresponding equipment.

Once the edges of the part has been sanded using the abrasive methodsdescribed herein, the face of the part is then ready to be sanded inaccordance with abrasive methods demonstrated in FIGS. 3, 6, and 8. Themost common machinery employed is one (or a combination) of thefollowing: a wide belt sander, a wide belt veneer segmented platensander, a wide orbital machine sander, a random orbital hand sander. Ina preferred embodiment, the method employs the wide belt veneersegmented platen sander and wide orbital machine sander operated intandem. Abrasive grit size and sequence is important to this process andvaries based upon the abrasive manufacturer and the specific sandingequipment being used. In a preferred embodiment, abrasives with aminimum of 15μ grit size should be used in this step to accomplishproper adhesion of the liquid top coat during the final liquid top coatstep. A diagram of preferred embodiment grit size and sequences for thisstep is set forth in FIG. 13, broken out by sanding equipment beingused.

In a preferred embodiment, wide belt veneer segmented platen sanderswith the Cross Belt Finish (CBF) technology are employed when sandingthe face; this equipment is preferred because it results in the mostreliable outcome with the least amount of fallout and required rework,as shown in FIGS. 4-5. This CBF technology is the preferred, but not theonly, wide belt veneer segmented platen sander technology that will workfor the present invention.

It is possible that a variety of other face and edge sanding (or othersurface smoothing) equipment could be utilized while remaining withinthe scope of the invention, however the specific equipment listed hereinhas been tested for repeatable success. Further, it is possible toachieve a lesser quality finish (but still smoother than untreatedpowder coated MDF) using a variety of other equipment, grits, sequences,and process order changes (such as sanding the face before the edges).For example, a PCI smoothness of 7-8 is sporadically possible usingdifferent grits and sequences, whereas a PCI smoothness of 8-10 isroutinely and reliably attainable using the method described herein.

Once the face and edges achieve the desired smoothness as shown in FIG.9, the part is ready to accept a liquid top coat. The application ofliquid top coat will now be discussed. The liquid top coat should beapplied according to manufacturer directions and in a preferredembodiment should be applied to a minimum thickness of 2 wet mils; somevariation in final thickness is created by the type of liquid finishused and the application process. An inferior finish can be obtainedusing top coat coverage of less than 2 wet mils. Automated processestypically receive 2 wet mils of coverage, and manual processes typicallyreceive 3-5 wet mils of coverage. In a preferred embodiment, severalspecific steps should be taken as part of the liquid top coat step ofthis described process:

-   -   The entire part is wiped using a lint free towel and isopropyl        alcohol.    -   The surface is deionized to avoid attraction of dust and other        foreign particles. Otherwise the final top coat may be        contaminated.    -   One coat is sufficient for automated or manual application        processes, however two coats can be applied for a more robust or        lustered finish. Light sanding is necessary if a second coat is        applied.

See FIG. 14 for a diagram of several liquid top coats that have beentested for use in the invention. Although this is not a comprehensivelist of all liquid top coats that will work with the invention, it isranked in order of desirability of those currently tested for use withthe process. In a preferred embodiment, pre-catalyzed lacquers orpost-catalyzed conversion varnishes are used as the liquid top coat.Furthermore, although the examples described herein often refer to clearliquid top coats, it is not essential to the success of the inventionthat the liquid top coat explicitly be clear in color. For example,tinted liquid top coats or those containing color pigments can also worksuccessfully with the invention.

A top coat applied to powder coated MDF, without the specific treatmentsoutlined in this application, would result in a similar PCI smoothnessnumber as the untreated part. Simply sanding the powder coated MDF part,without application of a top coat, will result in a “chalky”, delicatefinish that does not have the durability characteristics of either theuntreated or final top coated part. Furthermore, a wide variety ofabrasive grit numbers and sequences have been tested; those grit numbersand sequences not outlined in this application either result in lessersmoothness ratings or result in a coating failure. The only known methodto improve PCI smoothness of a powder coated MDF finish is to follow thepre- and post-coating steps as well as the abrasive grit number andsequences outlined in this application.

Example 1

A sheet of powder coat grade MDF is cut by a CNC router with newcondition solid carbide tooling into a rectangle with dimensions of12″W, 18″L, 0.75″ thickness. Edge profiles are shaped to 1/16″ radiusand the part is sanded using an automated sanding machine. The part ispowder coated to a thickness of 8 mils using a white epoxy thermosetpowder. At this point, the powder coated part has a PCI smoothness of5-6. After powder coating, the coated part is sanded with a veneersegmented platen sander and wide orbital machine sander operated intandem. An abrasive grit sequence is followed with the correspondingpiece of equipment as represented in FIG. 15.

After the above sanding sequences, a 5 mil 85 degree gloss pre-catalyzedclear lacquer top coat is manually applied to the part. The resultingpart has a PCI smoothness of 10 and the visual depth of a 5-coat wetsanded liquid paint finish.

Comparative Example 1a

A sheet of powder coat grade MDF is cut by a CNC router with newcondition solid carbide tooling into a rectangle with dimensions of12″W, 18″L, 0.75″ thickness. Edge profiles are shaped to 1/16″ radiusand the part is sanded using an automated sanding machine. The part ispowder coated to a thickness of 8 mils using a white epoxy thermosetpowder. At this point, the powder coated part has a PCI smoothness of5-6. Without first sanding the powder coated part, a 5 mil 85 degreegloss pre-catalyzed clear lacquer top coat is manually applied. Theresulting part has an unchanged PCI smoothness of 5-6.

Comparative Example 1b

A sheet of powder coat grade MDF is cut by a CNC router with newcondition solid carbide tooling into a rectangle with dimensions of12″W, 18″L, 0.75″ thickness. Edge profiles are shaped to 1/16″ radiusand the part is sanded using an automated sanding machine. The part ispowder coated to a thickness of 8 mils using a white epoxy thermosetpowder. At this point, the powder coated part has a PCI smoothness of5-6. After powder coating, the coated part is sanded with a veneersegmented platen sander and wide orbital machine sander operated intandem. An abrasive grit sequence is followed with the correspondingpiece of equipment as represented in FIG. 15.

However, unlike example 1, this part is left without the application ofa clear liquid top coat. The resulting part has a PCI smoothness of9-10; however, the gloss level cannot be controlled and the finish ischalky. It would not hold up to any end-product use without furthersurface treatment, and has no discernible finish depth. While thepresent invention has been fully described above with particularity anddetail in connection with what is presently deemed to be the mostpractical and preferred embodiment of the invention, it will be apparentto those of ordinary skill in the art that numerous modifications,including, but not limited to, variations in size, materials, shape,form, function and manner of operation, assembly and use may be made,without departing from the principles and concepts of the invention asset forth in the claims.

The invention claimed is:
 1. A powder coated article having enhancedvisual and tactile smoothness, the article comprising: a substrate of adesired size containing wood having radiused edges that have a minimumradius of one thirty second of an inch (0.8 mm); a cured powder coatsurface coating overlying the substrate, the powder coat surface coatingbeing at least 5 mils in thickness and having a PCI smoothness of atleast 6; a cured liquid top coat overlying the powder coat surfacecoating, the cured liquid topcoat having a PCI smoothness of at least 8and having been applied to a minimum top coat thickness of 2 wet mils;and wherein a resulting finish has improved PCI smoothness and improvedvisual and tactile smoothness as compared to a similar powder coatedpart without the cured liquid top coat.
 2. The powder coated article asclaimed in claim 1, wherein the substrate comprises medium-densityfiberboard (MDF).
 3. The powder coated article as claimed in claim 1,wherein the substrate comprises high-density fiberboard (HDF).
 4. Thepowder coated article as claimed in claim 1, wherein the powder coatsurface coating comprises an ultraviolet cured powder coating material.5. The powder coated article as claimed in claim 1, wherein the curedliquid top coat comprises a pre-catalyzed lacquer.
 6. The powder coatedarticle as claimed in claim 1, wherein the cured liquid top coatcomprises a post-catalyzed conversion varnish.
 7. The powder coatedarticle as claimed in claim 1, wherein the cured liquid top coatcomprises an incorporated color pigment.
 8. The powder coated article asclaimed in claim 1, wherein at least one surface of the substrate ismachined to a tolerance of less than 0.030 inches.
 9. A powder coatedarticle of manufacture, comprising: a wood based substrate of a desiredsize and shape having radiused edges that have a minimum radius of onethirty second of an inch (0.8 mm); an inner coating layer of fusedpowder coating overlying and bonded to the wood based substrate, theinner coating layer having a thickness of at least 5 mils and a PCIsmoothness of at least 6; and an outer coating layer of cured liquidfinish overlying and bonded to the layer of powder coating.
 10. Thepowder coated article of manufacture as claimed in claim 9, wherein thewood based substrate has at least one surface that is machined to atolerance of less than 0.030 inches.
 11. The powder coated article ofmanufacture as claimed in claim 9, wherein the outer coating layer has aPCI smoothness of at least
 8. 12. The powder coated article ofmanufacture as claimed in claim 9, wherein the wood based substratecomprises medium-density fiberboard (MDF).
 13. The powder coated articleof manufacture as claimed in claim 9, wherein the wood based substratecomprises high-density fiberboard (HDF).
 14. The powder coated articleof manufacture as claimed in claim 9, wherein the inner coating layercomprises an ultraviolet cured powder coating material.
 15. The powdercoated article of manufacture as claimed in claim 9, wherein outercoating layer comprises a pre-catalyzed lacquer.
 16. The powder coatedarticle of manufacture as claimed in claim 9, wherein outer coatinglayer comprises a post catalyzed conversion varnish.
 17. The powdercoated article of manufacture as claimed in claim 9, wherein outercoating layer comprises an incorporated color pigment.
 18. The powdercoated article of manufacture as claimed in claim 9, wherein outercoating layer has PCI smoothness of 10 and a visual depth equivalent toa five coat wet sanded liquid paint finish.
 19. The powder coatedarticle of manufacture as claimed in claim 9, wherein the inner coatinglayer of powder coating has a thickness of 7 to 8 mils.